Gradient optics for even light distribution of led light sources

ABSTRACT

Gradient optics for even light distribution of LED light sources. In an aspect, an apparatus is provided for uniform distribution of light emitted from a light source. The apparatus includes a panel coupled to receive the light emitted from the light source, and gradient optics disposed on the panel, the gradient optics providing a matching transparency gradient that is aligned with the light source to evenly distribute the emitted light. In another aspect, an apparatus includes means for receiving the light emitted from the light source, and means for providing a matching transparency gradient that is aligned with the light source to evenly distribute the emitted light.

CROSS-REFERENCE TO RELATED APPLICATION

This Application claims priority to U.S. Provisional Application Ser.No. 61/427,740, filed Dec. 28, 2010, the contents of which are herebyincorporated by reference herein their entirety.

BACKGROUND Field

The present application relates generally to light emitting diodes, andmore particularly, to gradient optics for even light distribution of LEDlight sources.

A light emitting diode comprises a semiconductor material impregnated,or doped, with impurities. These impurities add “electrons” and “holes”to the semiconductor, which can move in the material relatively freely.Depending on the kind of impurity, a doped region of the semiconductorcan have predominantly electrons or holes, and is referred to as ann-type or p-type semiconductor region, respectively.

In LED applications, an LED semiconductor chip includes an n-typesemiconductor region and a p-type semiconductor region. A reverseelectric field is created at the junction between the two regions, whichcauses the electrons and holes to move away from the junction to form anactive region. When a forward voltage sufficient to overcome the reverseelectric field is applied across the p-n junction, electrons and holesare forced into the active region and combine. When electrons combinewith holes, they fall to lower energy levels and release energy in theform of light. The ability of LED semiconductors to emit light hasallowed these semiconductors to be used in a variety of lightingdevices. For example, LED semiconductors may be used in general lightingdevices for interior or exterior applications.

A troffer is a light fixture resembling an inverted trough that iseither recessed in, or suspended from, the ceiling. Troffers aretypically designed to emit light using fluorescent lighting tubes. Thefluorescent tubes emit light along the entire length of the troffer toproduce a desirable light distribution pattern. Unfortunately,fluorescent lighting tubes may be expensive, require a warm up period,and produce flicker that people may find undesirable. Thus, LEDs areattractive candidates for replacing fluorescent lighting tubes introffers. For example, LEDs have no warm up time, are long lasting andpower efficient, and do not flicker. However, LEDs are considered to bea point light source in that the light is emitted from a relativelysmall region. Thus, utilizing LEDs in troffers present various designchallenges since it is desirable to have uniformly distributed lightacross the length of the Troffer. One technique for using LEDs to obtainuniformly distributed light across the length of the Troffer is to use alarge number of LEDs that are distributed throughout the troffer.Unfortunately, this technique results in a complex troffer design andthe cost of utilizing a large number of LEDs may be prohibitive.

Accordingly, what is needed is a simple and cost efficient way toprovide even light distribution for point light sources therebyfacilitating the use of LED semiconductors in troffer devices.

SUMMARY

In various aspects, a distribution panel is provided that operates toproduce uniformly distributed light from various light sources. Forexample, the distribution panel is suitable for use in a troffer deviceto provide even distribution of light emitted from LED semiconductors.The distribution panel comprises gradient optics providing a matchingtransparency gradient that is matched to a light source to uniformlydistribute the emitted light. As a result, the distribution panel candistribute the light from a few LED devices or a fluorescent tube acrossan entire troffer. Thus, the distribution panel with matchingtransparency gradient provides a simple and cost efficient way toutilize LED semiconductors in a troffer to produce uniformly distributedlight.

In one implementation, an apparatus is provided for uniform distributionof light emitted from a light source. The apparatus comprises a panelcoupled to receive the light emitted from the light source, and gradientoptics disposed on the panel, the gradient optics providing a matchingtransparency gradient that is aligned with the light source to evenlydistribute the emitted light.

In another implementation, an apparatus is provided for uniformdistribution of light emitted from a light source. The apparatuscomprises means for receiving the light emitted from the light source,and means for providing a matching transparency gradient that is alignedwith the light source to evenly distribute the emitted light.

It is understood that other aspects of the present invention will becomereadily apparent to those skilled in the art from the following detaileddescription. As will be realized, the present invention includes otherand different aspects and its several details are capable ofmodification in various other respects, all without departing from thespirit and scope of the present invention. Accordingly, the drawings andthe detailed description are to be regarded as illustrative in natureand not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects described herein will become more readily apparentby reference to the following Description when taken in conjunction withthe accompanying drawings wherein:

FIG. 1 shows an exemplary apparatus that illustrates the operation of adistribution panel with matching transparency gradient to provide evenlight distribution;

FIG. 2 shows a detailed top view of the distribution panel shown in theapparatus of FIG. 1;

FIG. 3 shows various implementations of the distribution panel shown inFIG. 2 constructed in accordance with the present invention;

FIG. 4 shows a distribution panel with matching transparency gradient toevenly distribute light in a troffer device that includes a fluorescenttube;

FIG. 5 shows a distribution panel with matching transparency gradientsto evenly distribute light in a troffer device that includes four LEDsemiconductors;

FIG. 6 shows the components illustrated in FIG. 5 in a completed LEDtroffer assembly; and

FIG. 7 shows an exemplary distribution apparatus with matchingtransparency gradient.

DESCRIPTION

The present invention is described more fully hereinafter with referenceto the accompanying drawings, in which various aspects of the presentinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to the variousaspects of the present invention presented throughout this disclosure.Rather, these aspects are provided so that this disclosure will bethorough and complete, and will fully convey the scope of the presentinvention to those skilled in the art. The various aspects of thepresent invention illustrated in the drawings may not be drawn to scale.Accordingly, the dimensions of the various features may be expanded orreduced for clarity. In addition, some of the drawings may be simplifiedfor clarity. Thus, the drawings may not depict all of the components ofa given apparatus (e.g., device) or method.

Various aspects of the present invention will be described herein withreference to drawings that are schematic illustrations of idealizedconfigurations of the present invention. As such, variations from theshapes of the illustrations as a result, for example, manufacturingtechniques and/or tolerances, are to be expected. Thus, the variousaspects of the present invention presented throughout this disclosureshould not be construed as limited to the particular shapes of elements(e.g., regions, layers, sections, substrates, etc.) illustrated anddescribed herein but are to include deviations in shapes that result,for example, from manufacturing. By way of example, an elementillustrated or described as a rectangle may have rounded or curvedfeatures and/or a gradient concentration at its edges rather than adiscrete change from one element to another. Thus, the elementsillustrated in the drawings are schematic in nature and their shapes maynot be intended to illustrate the precise shape of an element and arenot intended to limit the scope of the present invention.

It will be understood that when an element such as a region, layer,section, substrate, or the like, is referred to as being “on” anotherelement, it can be directly on the other element or intervening elementsmay also be present. In contrast, when an element is referred to asbeing “directly on” another element, there are no intervening elementspresent. It will be further understood that when an element is referredto as being “formed” on another element, it can be grown, deposited,etched, attached, connected, coupled, or otherwise prepared orfabricated on the other element or an intervening element.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother element as illustrated in the drawings. It will be understoodthat relative terms are intended to encompass different orientations ofan apparatus in addition to the orientation depicted in the Drawings. Byway of example, if an apparatus in the Drawings is turned over, elementsdescribed as being on the “lower” side of other elements would then beoriented on the “upper” sides of the other elements. The term “lower”,can therefore, encompass both an orientation of “lower” and “upper,”depending of the particular orientation of the apparatus. Similarly, ifan apparatus in the drawing is turned over, elements described as“below” or “beneath” other elements would then be oriented “above” theother elements. The terms “below” or “beneath” can, therefore, encompassboth an orientation of above and below.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andthis disclosure.

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. The term “and/or” includes any andall combinations of one or more of the associated listed items

It will be understood that although the terms “first” and “second” maybe used herein to describe various regions, layers and/or sections,these regions, layers and/or sections should not be limited by theseterms. These terms are only used to distinguish one region, layer orsection from another region, layer or section. Thus, a first region,layer or section discussed below could be termed a second region, layeror section, and similarly, a second region, layer or section may betermed a first region, layer or section without departing from theteachings of the present invention.

FIG. 1 shows an exemplary apparatus 100 that illustrates the operationof a distribution panel with matching transparency gradient to provideeven light distribution. The apparatus 100 comprises a housing 102, LEDlight source 104 and distribution panel 106 with matching transparencygradient.

During operation, light emitted from the LED 104 strikes thedistribution panel 106 and the matching transparency gradientdistributes the light to produce even light distribution, showngenerally at 110.

The panel 106 is designed to have a matching transparency gradient thatis orientated and/or aligns or matches the location of the LED 104. Forexample, the panel 106 provides less transparency at a center linelocation directly below the LED 104 and increasing transparencycorresponding to increasing distances from the center line. Thus, morelight passes through the panel 106 at positions located radially outwardfrom the center line. As a result, even light distribution as shown at110 can be achieved. A more detailed description of the distributionpanel 106 is provided below.

To enhance the light distribution properties of the distribution panel106, the housing 102 comprises reflective surfaces, shown generally at112. The reflective surfaces 112 operate to reflect light back throughthe distribution panel to enhance its light distribution properties. Forexample, direct light 108 strikes the distribution panel and some ofthis direct light is reflected. This light then travels back up to thereflective surfaces 112 where is it reflected back through thedistribution panel 106. The light rays shown generally at 114 illustratethe path of the reflected light. Therefore, the apparatus 100illustrates the operation of the distribution panel 106 to provide evenlight distribution from an LED light source.

FIG. 2 shows a detailed top view of the distribution panel 106 shown inFIG. 1. The distribution panel 106 provides a transparency gradient toenable even distribution of light from a point source. In oneembodiment, the distribution panel 106 is made from an acrylic orplastic material having concentric circles 202 that vary the materialdensity with the radial distance between the circles increasing as theradial distance from a point directly below the LED 104 increases. Thevarying material densities of the concentric circles 202 providedifferent transparency characteristics so that a transparency gradientis formed such that greater transparency is provided at the outercircles than the inner circles. For example, thicker material allowsless light to pass through. Thus, tightly packed rings make the materialdenser in the center and less dense at edges.

A graph 204 illustrates the transparency gradient provided by thedistribution panel 106. The graph 204 comprises a plot line 206representing the transparency of the distribution panel 106 at anylocation on the indicator line 208. As shown in the graph 204, moretransparency is provided at the outer circles indicated at 210 and lesstransparency is provided at the inner circles as indicated at 212.

FIG. 3 shows cross sectional views of various implementations of thedistribution panel 106 constructed in accordance with the presentinvention. For example, the cross sectional views are taken at crosssection indicator 208 shown in FIG. 2. Each implementation comprises apanel with gradient optics disposed thereon.

In a first implementation 302, the distribution panel 106 comprises apiece of acrylic and the gradient optics 306 comprise concentric circles(illustrated at 308) of varying diameter whose centers are aligned andlocated on center line 304. When in use, the center line 304 also alignswith the LED semiconductor whose emitted light is being distributed bythe distribution panel 106. The concentric circles of material may havethe same or different thicknesses. Thus, the thickness of the panel 106decreases with increasing distance from the center line 304. Theincreasing thickness provides the transparency gradient illustrated at324. It should be noted that the gradient optics 306 are not limited tocircles or any particular geometric shape. Furthermore, although shownas increasing the material thickness of the panel, the gradient optics306 may comprise material of varying densities which do not change thematerial thickness but accomplish the same result.

In a second implementation 310, the distribution panel 106 comprises apiece of acrylic and the gradient optics 312 comprise a surface coatingthat provides the transparency gradient. The surface coating may beformed using a variety of techniques. For example, the surface coatingmay be a diffuser film applied to the acrylic or a polymer material thatis painted onto the acrylic. The surface coating is designed to provideless transparency near the center line 304, as illustrated by the darkregion 314, and more transparency as the distance from the center lineincreases, as illustrated at the light region 316. The differenttransparency regions of the surface coating provide the transparencygradient illustrated at 324.

In a third implementation 318, the distribution panel 106 comprises apiece of acrylic and the gradient optics 320 comprise surface texturingthat provides one or more surface features 322. The surface features 322may be ridges, bumps or other surface features that are arranges in anydesired pattern and/or spacing to provide the transparency gradientillustrated at 324. For example, in one implementation, the surfacetexturing comprises rings of ribs that gradually increase in diameterfrom the center line 304.

In a fourth implementation 326, the distribution panel 106 comprises apiece of acrylic and the gradient optics 328 comprise surface texturingthat provides one or more surface defects, as illustrated at 330. Thesurface defects 330 comprise scratched or sanded regions or otherdefects in the acrylic panel which affect light distribution. Thesurface defects are arranged in any desired pattern and/or spacing toprovide the transparency gradient illustrated at 324. For example, moresurface defects are shown toward the center line 304, as illustrated at332, to reduce transparency. Less surface defects are provided as thedistance from the center line 304 increases to increase transparency.

Therefore, the various implementations of the distribution panel 106provide a transparency gradient that evenly distributes light from alight source. It should be noted that although four types of gradientoptics are shown, any suitable type of technique or optical mechanismmay be used to provide gradient optics allowing the transparencygradient 324 to be produced. It should also be noted that the variousgradient optic may be used individually or combined in any combinationor fashion to produce the transparency gradient 324.

FIG. 4 shows a distribution panel 400 with matching transparencygradient configured to evenly distribute light in a troffer device thatincludes a fluorescent tube. The distribution panel 400 comprisesgradient optics that provide a transparency gradient aligned alongcenter line 402, which matches a center line along the length of thefluorescent tube. For example, the gradient optics comprise lesstransparency at location 404 and increased transparency as the distancefrom the center line 402 increases, for instance, at location 406.

Also shown in FIG. 4 is end view 410 of the distribution panel 400. Forexample, the end view 410 is taken at cross section indicator 408. Theend view 410 illustrates how the gradient optics provide thickermaterial for less transparency at location 404, and less material toprovide greater transparency at location 406.

Thus, the distribution panel 400 provides a matching transparencygradient configured to evenly distribute light in a troffer device thatincludes a fluorescent tube.

FIG. 5 shows a distribution panel with matching transparency gradient toevenly distribute light in a troffer device that includes four LEDsemiconductors. A troffer 500 comprises a housing 502 that isillustrated in side 504, bottom 506 and end 508 views. For example, thehousing may be a 2′×4′ housing typically used for fluorescent lighting.

Referring to the side view 504, the housing 502 comprises an internalreflective surface 510 which is designed to reflected light to thebottom portion of the housing. Referring to the end view 508, thereflective surface 510 is more clearly shown.

Referring now to the bottom view 506, the housing 502 comprises four LEDsemiconductor devices 512 mounted therein. The LEDs 512 are spaced alongthe length of the housing 502 and are configured to emit light towardthe bottom of the housing 502.

The troffer 500 also comprises a distribution panel 514 which is shownin the bottom view 510. The distribution panel 514 comprises fourtransparency gradients 516 that are matched to align with each of theLEDs 512. When assembled to the housing 502, the distribution panel 514operates to evenly distribute light emitted from the LEDs 512.

It is also possible that additional LEDs (or LED arrays) each associatedwith their own transparency gradient on the distribution panel 514 beadded to the housing 502 to better spread out the light over largerareas. By way of example, the troffer 500 may be divided into any numberof regions with an LED (or LED array) mounted at the center of eachregion and having a distribution panel with matching transparencygradient associated with each LED.

FIG. 6 shows the components illustrated in FIG. 3 in a completed trofferassembly 600. For example, the troffer assembly 600 is suitable for useas an internal lighting device, such as a ceiling light. In the trofferassembly 600, the distribution panel 514 is mounted to the bottomportion of the housing 502. It should be noted that the distributionpanel 514 provides a matching transparency gradient for each LED byutilizing concentric circles of material to increase transparency as thedistance from a center line through each LED increases.

During operation, each of the LEDs 512 emit light that passes throughtheir associated matched transparency gradients provided by thedistribution panel 514 to produce evenly distributed light illustratedat 602.

Light from the LEDs 512 also reflects off the reflective surface 510 toenhance the light distribution effects of the distribution panel 514.Thus, the troffer assembly 600 operates to provide evenly distributedlight from an LED light source that overcomes the problems associatewith convention fluorescent lighting.

FIG. 7 shows an exemplary distribution apparatus 700 with matchingtransparency gradient. For example, the apparatus 700 is suitable foruse as the distribution panel 106 shown in FIG. 2.

The distribution apparatus 700 comprises a first means (702) forreceiving light emitted from a light source, which in an aspectcomprises the panel 106.

The distribution apparatus 700 also comprises a second means (704) forproviding a matching transparency gradient that is aligned with thelight source to evenly distribute the emitted light.

Thus, the distribution apparatus 700 provides a matching transparencygradient to provide for uniform light distribution.

The various aspects of this disclosure are provided to enable one ofordinary skill in the art to practice the present invention. Variousmodifications to aspects presented throughout this disclosure will bereadily apparent to those skilled in the art, and the concepts disclosedherein may be extended to other applications. Thus, the claims are notintended to be limited to the various aspects of this disclosure, butare to be accorded the full scope consistent with the language of theclaims. All structural and functional equivalents to the elements of thevarious aspects described throughout this disclosure that are known orlater come to be known to those of ordinary skill in the art areexpressly incorporated herein by reference and are intended to beencompassed by the claims.

Moreover, nothing disclosed herein is intended to be dedicated to thepublic regardless of whether such disclosure is explicitly recited inthe claims. No claim element is to be construed under the provisions of35 U.S.C. §112, sixth paragraph, unless the element is expressly recitedusing the phrase “means for” or, in the case of a method claim, theelement is recited using the phrase “step for.”

Accordingly, while aspects of a distribution panel with matchingtransparency gradient have been illustrated and described herein, itwill be appreciated that various changes can be made to the aspectswithout departing from their spirit or essential characteristics.Therefore, the disclosures and descriptions herein are intended to beillustrative, but not limiting, of the scope of the invention, which isset forth in the following claims.

What is claimed is:
 1. An apparatus for uniform distribution of lightemitted from a light source, the apparatus comprising: a panel coupledto receive the light emitted from the light source; and gradient opticshaving varying transparency disposed on the panel, wherein the gradientoptics align with the light source to evenly distribute the light. 2.The apparatus of claim 1, wherein the gradient optics further align witha center line through the light source so that the panel providesincreasing transparency as a distance from the center line increases. 3.The apparatus of claim 2, wherein the gradient optics compriseconcentric regions of material that are disposed on the panel so that atleast one of panel thickness and material density decreases as thedistance from the center line increases.
 4. The apparatus of claim 2,wherein the gradient optics comprise a coating that is disposed on thepanel so that the panel provides increasing transparency as the distancefrom the center line increases.
 5. The apparatus of claim 2, wherein thegradient optics comprise surface texturing disposed on the panel so thatthe panel provides increasing transparency as the distance from thecenter line increases.
 6. The apparatus of claim 5, wherein the surfacetexturing comprises surface features that provide increasingtransparency as the distance from the center line increases.
 7. Theapparatus of claim 5, wherein the surface texturing comprises surfacedefects that provide increasing transparency as the distance from thecenter line increases.
 8. The apparatus of claim 1, wherein the panelcomprises at least one material selected from a set of materialscomprising acrylic, plastic, crystal, glass, and polymer materials. 9.The apparatus of claim 1, wherein the light source comprises one or morelight emitting diodes (LEDs) and the gradient optics provide one or morematching transparency gradients, respectively, wherein each matchingtransparency gradient aligns with a center line associated with arespective LED.
 10. The apparatus of claim 9, wherein the one or moreLEDs are mounted in a troffer and the panel is sized to fit the trofferto provide uniform light distribution.
 11. The apparatus of claim 1,wherein the light source comprises a fluorescent tube and the gradientoptics align with a center line located along the length of thefluorescent tube.
 12. The apparatus of claim 11, wherein the fluorescenttube is mounted in a troffer and the panel is sized to fit the trofferto provide uniform light distribution.
 13. An apparatus for uniformdistribution of light emitted from a light source, the apparatuscomprising: means for receiving the light emitted from the light source;and means for providing gradient optics having varying transparency,wherein the gradient optics align with the light source to evenlydistribute the light.
 14. The apparatus of claim 13, wherein the meansfor providing comprises means for aligning the gradient optics with acenter line through the light source to provide increasing transparencyas a distance from the center line increases.
 15. The apparatus of claim14, wherein the means for providing further comprises means forproviding the gradient optics utilizing at least one of materialthickness, material density, surface coating, and surface texturing toprovide increasing transparency as the distance from the center lineincreases.
 16. The apparatus of claim 13, wherein the means forproviding comprises means for providing the gradient optics utilizing atleast one material selected from a set of materials comprising acrylic,plastic, crystal, glass, and polymer materials.
 17. The apparatus ofclaim 13, wherein the light source comprises one or more light emittingdiodes (LEDs) and the means for providing comprises means for providingone or more matching transparency gradients, respectively, wherein eachmatching transparency gradient aligns with a center line associated witha respective LED.
 18. The apparatus of claim 17, wherein the one or moreLEDs are mounted in a troffer and the apparatus is sized to fit thetroffer to provide uniform light distribution.
 19. The apparatus ofclaim 13, wherein the light source comprises a fluorescent tube and themeans for providing comprises means for providing the gradient optics toalign with a center line located along the length of the fluorescenttube.
 20. The apparatus of claim 19, wherein the fluorescent tube ismounted in a troffer and the apparatus is sized to fit the troffer toprovide uniform light distribution.